1 Answer
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Machine Name Formats
NFS clients may be specified in a number of ways:
[...]
IP networks
You can also export directories to all hosts on an IP (sub-) network
simultaneously. This is done by specifying an IP address and netmask pair
as address/netmask where the netmask can be specified in dotted-decimal
format, or as a contiguous mask length. For example, either
`/255.255.252.0' or `/22' appended to the network base IPv4 address
results in identical subnetworks with 10 bits of host. [...]
Wildcard characters generally do not work on IP addresses, though they
may work by accident when reverse DNS lookups fail.
wildcards
Machine names may contain the wildcard characters * and ?, or may contain
character class lists within [square brackets]. This can be used to make
the exports file more compact; for instance, *.cs.foo.edu matches all
hosts in the domain cs.foo.edu. As these characters also match the dots
in a domain name, the given pattern will also match all hosts within any
subdomain of cs.foo.edu.

This simply means you're configuring it wrong in the line

/myshare 192.168.1.*(rw,sync,no_subtree_check)

Wildcards can be used in hostnames, for specifying IP networks, you need to use dotted-decimal IP addresses and an optional subnet size. The reverse IP-lookup story above could explain why it worked for a specific address.